My car threw 2 codes the other day one was a p0442- small evap leak and a p0430 catalyst efficiency below threshold bank 2. I fixed the evap by replacing the gas cap and hose on the plenum to the canister purge was cracking apart but 100 miles later the p0430 is back. I left the Genisys on it and drove around a bit and I noticed when I first start it the pre-cat 02 on bank 2 is at negative voltage and takes quite a while to climb up to match bank 1 and at times it seems to stick on one voltage while the other changes around. Also at times it shows 0.0v or -0.01v so I am thinking it maybe the front left 02 is going as the cats are not that old, I did not do them so I cannot speak for miles. Anyone else had this and fixed it with an 02 or should I just buy cats and skip right to the expensive part??

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

Test the downstream HO2s. 430 says catalyst efficiency below threshold, so if your downstream O2 sensor were working properly then it's reporting back that the catalytic converter isn't storing the proper amount of oxygen. If you're feeling randy, swap downstream HO2S bank 2 with bank 1, erase the codes and wait for the code to come back. If it jumped to bank 1 then the HO2S is at fault. If it sticks on bank 2 then your cat isn't up to par. The upstream HO2S are responsible for fuel mapping and the downstream is there for reference as to whether the catalyst is efficient enough or not. This is the jist I get from it. From what I have learned from experience? DON'T replace it until you've tested it and found it faulty. I've wasted far too much money on stupid expensive sensors without testing them properly first.

I am going to replace the one pre-cat 02 on the left because yesterday a few times it kept showing 0 volts and then would stay at .38v for long periods of time while the other kept switching back and forth voltage wise. I figure it is the $38 try first and if I do need cats then I will do it next. I crawled under and looked at the cats and they are dated 4-08 and that really $ucks because from the little background I know on this car they have maybe 9k miles on them as it sat for almost all of 2009 into 2010. The inspection stickers on it when I got it expired in 3/2010 and when they were done 2/2009 the car had 108,800 miles and when I got it 109,900 and the guy I got it from had it sitting for about 8 months so they were only used about 10 months max depending on how long they sat on the shelf before installation.

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

I finally replaced my front 02 sensors today with nice, new Motorcraft ones, took about 35 minutes start to finish for both sides so not bad at all. I put up a picture of the left one that kept showing 0 and negative voltage readings and I believe it was the cause of the P0430 code judging by the shape of the wires on it. I am guessing it was caused by the engine/trans combo being installed and it smacking the wires on the way in as it was a bit tight. I am now getting good voltage readings out of both front 02 sensors but the P0442 small evap leak code is back so I need to use the smoke machine and see what is going on there next. Also car had one Bosch 02 (the damaged one) and one Ford 02 so I doubt that was helping either.

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

Lasted about 30 miles and coding again for cat inefficiency, oh well. Now onto cats, I am looking at direct fit Walker Ultras for $180 each from Amazon shipped. Anyone else used these with good results??

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

Do you have access to Mode $06 PIDs of the ECM? If so, there is a PID called Index Ratio - this parameter counts number of switches of the rear O2 sensor vs. the front one (for each bank). On the properly working system (cat) the ratio is close to zero (rear O2 almost never switches - always full of oxygen, where the front one switches with engine operation as cylinders fire). The DTC threshold on my 2003 is 0.8 If your index ratio is greater than your threshold (also available in Mode $06) - the cat definitely can't keep up with emissions and DTC is set.

However, the reason may not be the cat itself. Factory manual names several reasons of this happening besides the cat.

One is misfire - if the car misfires too much, the unburnt fuel will end up in the cat, messing with its capabilities. Mode $06 will provide information on misfire rate for each cylinder as well as overall mis-fire rates for the engine.

Another reason is EGR - if the valve is stuck open - it would let exhaust in intake, messing with O2 content of the intake affecting the exhaust.

I believe so, I have an OTC Genisys scanner but I hoped when the front 02 on the left was just dropping out with no or negative voltage that was it. I got 2 Motorcraft 02 sensors for the upstream and changed them out but it made it about 30 miles and coding again. I doubt it is misfire as the entire engine including coils, plugs etc has only around 1600 or so miles on it from new and it seems to run fine and throws no other codes other than a random one for small evap leak and that comes and goes. Idle is dead smooth too so I would guess egr is working fine too. I think it is possible the old engine destroyed the cats from burning oil excessively, the one port on one of the old exhaust manifolds was 3/4 of the way closed up with crap I assume was oil burning. I will reconnect the scanner tonight and see what I can find out about mode $06 with it. I kinda resigned myself to the fact it needs cats, but, convincing the wallet of this has been a wee bit harder LOL.

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

Since you have a scan tool - you'd be able to figure out just about anything about the car.

Coincidently, I had the exact same two codes. I'd gone through the troubleshooting steps and took it to the dealer all leading to conclusion of bad cat. In my case, the EVAP code was the leaky valve under the gas tank, and the Cat code was the cat. One major symptom was that B2 tail pipe produced more smoke than the other one indicating the cat was not doing its job (despite the cross-pipe). Do you have that condition? Does the car run "dirty" on one side? If so, it's most likely the cat. Otherwise, all bets are off.

See what you can find out with mode $06. Ford (www.motorcraft.com) has the detailed description of all mode $06 PIDs and how to interpret them. It in PDF from under an OBD heading once you've selected your car.

I forgot to mention I can smell the exhaust just a bit with it idling and the door open so I am assuming cat or cats have failed or are failing. I just want to be sure I know why they failed so fast and fix it if necessary to prevent another rapid failure not covered by the warranty on the cats.

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

Here are some links to the Ford OBD-II System Operation Summary that you should find helpful. There is good info buried within the documents, if you spend the time wading through them and zero in on what's pertinent to your situation. I've included links to both the 2002 and 2008 model years because I don't know how the engine swap was handled with regards to the emmissions equipment. I hope it helps.

TID 10 CID 20 rear to front switch ratio bank2 max is 52 measured is 54. This number does not make sense - it a ratio from 0.0 to 1.0 for MY 2002. 2008 MY uses different algo for checking efficiency (as I am sure by now you've read in PDF)

TID 42 CID 11 no description max is 32673 measured is 32768is Pressure for upstream hose for the Differential Pressure sensor for the EGR in mm H20. One of your hoses going to the pressure sensing module may be defective and/or unplugged. Judging by other EGR (stuck open) problem - you may have DPFE EGR issues, which may affect Cat efficiency according to the manual. The only question here is that EGR failure would affect both banks... How is the Index Ratio (TID 10, CID 10 ) for the other Bank? Is it high, but below threshold?

How does TID 53 look? Any misfires? What about highest (TIDs 54 and 55)? Are all those 0.0?

BTW: looking at the TID values your PCM is for 2002 MY not 2008. There may have been changes in OBD monitoring strategy (and/or threshold values/sensor outputs) between the two years and your DTCs are not real. Is it possible?

Does your scan tool let you select Model Year of the car? Could you select different year (2008 instead of 2002 or vice versa)?

My entire electronics setup is all 2002, I basically used the long block from the 2008 and the water pump, pulley and crank balancer/pulley and that is pretty much it. Sorry for the confusion, my car is bastardo with different year stuff. All emissions/electrical is 2002 along with the trans and rear, drive belt stuff like timing cover, tensioner, idler etc is 1996-99, long block is 2008. I used what was available to me as I had a hard time finding stuff for anything past 99 local and the engine was from Ebay. I see where you are going with TID/CID 10 it may be low enough to not fail but right on the borderline indicating a problem. I will check DPFE hoses and sensor and possible switch out with a used set from the yard to see if I observe any changes good or bad. Thanks for the guidance with this!!! I do not use my scanner all that much as I do mostly GM vehicles and do so many I can almost tell just from the codes and few simple checks what is wrong. Ford is still a bit of a foreign language to me LOL.

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Sold the Vic and got a 94 GMC Sierra 4x4 stepside and a 2012 Scion XB.

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